The purpose of this study was (1) to compare South African bred opaque-2 (or high lysine) maize with normal maize in pig diets that contain an equivalent sub-optimum protein percentage and (2) to determine the protein sparing effect of a diet containing opague-2 maize when compared on a lysine equivalent basis with a diet containing normal maize and fish meal. Thirty six Landrace x Large White boars, initially 20 kg in mass, were fed ad libitum one of three experimental diets in a Latin square crossover experimental design over a 9-week period. Diet 1 (14% crude protein, normal maize), Diet 2 (14% crude protein,opaque-2 maize) and Diet 3 (15% crude protein. standard diet, normal maize, higher fishmeal content ) with lysine contents of 0,711%, 0,802,% and 0,828%, respectively, and an equivalent ME-content of l3 MJ/Kg. were used. Pigs fed the low protein, normal maize diet gained highly significantly less (between 8,1 and 9,7%) than pigs fed the other 2 diets which did not differ from each other. This diet was also less efficiently utilised than the other 2 diets to the extent of 6.9 to 7,9%. It was also established that 22% less fish meal can be used in the diet without influencing pig performance if opaque-2 instead of normal maize is used. These findings have clear economic implications in pig feeding.